Home Forums Hunting & Shooting Ask The Gunwriters Point of impact shifts over time?

So last weekend I pulled out my NULA .270 WBY which had been sitting in the safe since the end of wolf season last winter. Before putting it away back in January, I gave it a thorough cleaning, but that's it.

My first shot at the range was three inches higher than it should have been. The second shot went through the same hole, and the third cut the two.

I have a Swarovski Z5 3.5-18 with the ballistic turret on it. I pulled the BT off and adjusted down 3 MOA. Replaced it and fired another group which was dead on. I checked it at 220 and 360 yards, and it was spot on after the adjustment.

I've never really questioned why a rifle's point of impact changes over time. I just accepted that it does. With wood stocks, I always assumed that changes in humidity would cause the pressure on the action and barrel to change, resulting in POI shifts. But what I don't get is why this happens with synthetic guns. What really confuses me is that I have 7mm Rem Mag that was built by David Miller that I bought about 10 years ago. It hasn't changed zero the whole time. Every year I fire a group at the start of hunting season and it's right where I left it. My walnut stocked .375 Model 70 is pretty much the same way. That seems to blow my hypothesis out of the water.

Thoughts?

Scope?

After all, it's a variable... I mean we know it isn't supposed to move, but........

Cleaning will change the POI. My 300 WSM will change POI 4" right after a barrel swabbing. It takes 8-10 shots to foul the barrel for return to zero.

The scope has a zero-stop, I had it bottomed out. I've had rifles that need to be fouled, but this one shoots the same POI clean or dirty. Plus, it was sighted in clean last year.

I'm using this case more as an example. I guess my question is really from an overall standpoint, why do most rifles shift POI if you let them sit in the safe for an extended period of time? They're protected from the elements in a stable environment, not getting jostled and banged around etc. I can see it happening occasionally, but in my experience it happens more often than not, even with synthetic stocked guns.

A third factor in addition to the rifle and the scope is the ammunition. I believe that rounds from the same loading can shoot to a slightly different spot on another day.

Easy answer: scope gremlins. Makes me feel so good to be help full.

I've seen it with POS scopes. Nothing I could ever attribute to gun or ammo.

I have never seen a variable power scope as rock solid reliable over time in holding POI as a fixed power. I am talking years and enough rounds to cook the throat.

And.. the very reason bench shooters load at the event. Neck tensions change over time. Case lube sets hard in a glue like fashion and "holds" the bullet more firmly.

Ever used an inertia bullet puller on old ammo? Hard to remove aren't they?

Other than that, the scope is my pick. I don't care how much they cost, they can be problematic. When you chase accuracy and consistency, it is an automatic that you expect to junk scopes, especially variables.

Hope this helps.
John

Took me several years to realize that cleaning screws them up temporarily. A thorough cleaning and one chases zero for several rounds before it settles down. My 22 LR's are the worst, as it takes about 25 rounds for them to stop walking. Realized it after chasing zero and finding my scope right back on its original detents in two or three different sessions. Now I burn several rounds off target before even getting started.

Centerfires seem to be back in 2 or 3 rds.

Very good point.

By thorough cleaning did you take it out of the stock? If so it is possible/probable it changed POI.

Doesnt hold a zero....But the glass in is stunning!......



Given sound rings, bases, stock, bedding, ammo and scope, they don't shift zero.

After cleaning my 7x57AI it takes 3-5 rounds for it to hit where I want it to. The 5-15th or 20th shot will lay em in there. powdr

As a Kid I remember going to Camp Perry with my Uncle.He shot High power with a 03A3 and a Garand,At that time Lake City Match ammo was still made with corrosive primers.So at the end of the day everyone cleaned their rifles.We all slept in tents and about 5 AM you could hear all the guys taking fowling shots in the tents.It was a hell of a way to wake up!!!

Temperature change will change POA. Warmer it gets the higher pressures it creates. I have had that shooting factory loads too. Shot some Factory Winchester Power Point 150gr. in the 270WSM a couple weeks ago in 85 degree weather. Had primers crater and hard extraction.

LOL!

WELL, whadayakno? Really?
I posed this idea a few weeks back and got roasted!!
Camp Perry?

That's the catch. I had a Swaro variable once that behaved like the OP's....."had" and "once" are the operative words.

No more Swaro scopes for me.

A buddy just came in from preseason tuning on a dialed in and squeaky clean 270. Started chasing zero after 3 rds that were grouped about an inch left and 2 inches low. Fifteen rounds later, it was dialed in and back at it's original setting.